How to get my [solid mode] object OUTLINES back?
There are a couple places you can enable outlines. The first is within the viewport, to highlight selected and active objects. You can find that option here: 


The other is in the object properties, here:


Enable wire to see the black edge outlines regardless of selection. Enable "Draw All Edges" to display all edges, whether coplanar or not. By default, coplanar edges are not drawn.